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When a glass rod is rubbed with a silk cloth, the glass rod becomes positively charged. The reason for this is that

1. protons are transferred onto the rod
2. electrons are stripped away from the rod
3. electrons are transferred onto the rod
4. positively charged particles are deposited on the rod

Correct answer: electrons are stripped away from the rod

Solution

Charging by friction transfers only electrons because protons are bound in the nucleus and cannot move freely. When glass is rubbed with silk, electrons move from the glass to the silk; the glass, having lost electrons, is left with a net positive charge while the silk becomes negative.

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